A quantitative structure-activity correlation method has been designed to cover large amounts of data over diverse classes of compounds. The method is used to aid in selecting compounds for screening in mouse lymphocytic leukemia (P388). Estimates of activity, novelty, and, more recently, toxicity are based on P388 test results from over 50,000 compounds. The activity estimate is derived from the statistical significance of the incidence of each structural characteristic in the active compounds. The novelty estimate is based on the incidence of structural characteristics in previously tested compounds. These estimates are examined by the medicinal chemist along with the structures for about 30,000 potential acquisitions per year to decide which compounds to acquire. Active use of this process began in April 1980 after some experimentation to validate the method. Also a pilot run of a literature surveillance version was applied to one month's CAS registrations.